9. Renal Embryology

Question 1

What does the intermediate mesoderm produce?

Answer 1

Urinary (1st) and genital system

Question 2

What is the urogenital ridge?

Answer 2

Longitudinal bands of mesoderm that form on each side of the dorsal aorta

-forms nephrogenic cord (which forms pronephros, mesonephros, & metaphros)

Question 3

What is the order the nephrite structures form?

Answer 3

Urogenital ridge —> nephrogenic cord —> pronephros —> mesonephros —> metanephros

Question 4

What is the pronephros?

Answer 4

Bilateral, transitory structures that appear early in 4th week in cervical region

Degenerates by 24-25 days (except for the ducts)

IMP: bc they initiate cascade leading to formation of definitive kidney (w/o it nothing gets the ball rolling)

Question 5

Where are the pronephric ducts located

Answer 5

Run caudally & open into the cloaca

Persist & used by mesonephros

Question 6

What is the mesonephros?

Answer 6

Bilateral transient structure that appears later 4th week caudal to pronephros

-includes mesonephric ducts (made 1st) & mesonephric tubules (induced by ducts from surrounding intermediate mesoderm)

Question 7

What do the mesonophric tubules form?

Answer 7

Renal corpuscles

• medial end = glomerular capsule (cup-shaped)

& glomerulus (not of caps)

Question 8

What do the mesonephros do?

Answer 8

Fxn as interim kidneys from 6-10 weeks

• produce small amount of urine

Question 9

What happens to mesonephros after 10 weeks

Answer 9

Females - regress

Male- form efferent ductules

-degenerate by week 12

Question 10

What is the metanephros

Answer 10

-arise during 5th week at causal end of mesonephric duct —> induce ureteric bud

=ureteric bud & metanephric blastema

-form fxnal & definitive kidney by 9-10th week

Question 11

Where do the parts of the metanephros form

Answer 11

Ureteric bud - outgrowth of mesonephric ducts

Metanephric blastema = from sacral region of nephrogenic cord

Question 12

What is the purpose of urine production in utero

Answer 12

• makes amniotic fluid
• w/o = oligohydraminos —> potters sequence

Question 13

Where is waste filtered in embryo

Answer 13

Placenta

Question 14

How do the collecting tubules form

Answer 14

Ureteric bud elongate to sacral portion of intermediate mesoderm & penetrate the blastema —> form renal pelvis

-cranial part of buds —> collecting tubules - 1st generation = major calices & then 2nd = mini calices

Question 15

How does the nephron develop

Answer 15

Metanephrogenic blastema form metanephric vesicles

—> vesicles elongate to form metanephric tubules

—> proximal ends form glomerular capsule & get invaded by glomeruli

& other end of tubule differentiate into PCT, DCT and nephron loop –> then DCT contact arched collecting tubule

Question 16

How does the kidney ascend

Answer 16

permanent kidney lies w/I pelvis and gradually ascend into abd —> in adult position by 9th week & in contact with suprarenal glands

Question 17

How do the kidneys receive blood supply

Answer 17

First branch from common iliac & the definitive renal As from abdominal aorta

-early renal As & common iliac then involute and disappear

Question 18

Why does the hilum rotate medially 90 degrees

Answer 18

-allow correct orientation of vasculature

Question 19

What structures does the ureteric bud form

Answer 19

Ureter

Renal pelvis

Major & minor calyces

Collecting ducts

Question 20

What structures does the metanephric blastema form

Answer 20

Bowman’s capsule

PCT

Loop of hence

DCT

Question 21

what is the cause of unilateral renal agenesis & bilateral renal agenesis

Answer 21

ureteric bud doesn’t branch off mesenephros duct & doesnt induce metanephric blastema to from from sacral end

Question 22

what happens in duplication

Answer 22

abnormal divison of uretirc bud

incomplete = divide kindey & bifid ureter

complete = double kidney & bifid ureter/separate ureters

Question 23

what is horseshoe kidney

Answer 23

fusion of inferior poles

ascent prevented by inf mesenteric A & have low lying kidney

asym

Question 24

what are accessory renal vessels

Answer 24

multiple renal As

can obstruct the ureter by compressing it –> leading to hyrdonephrosis dilate pelvis & ureter –> filtrate backed up into kidney

get flank pain

also = end As so if damaged or ligated - can cause ischemia

Question 25

what is polycystic kidney disease

Answer 25

auto recessive mutation of PKHD1

cysts present in both kindeys

renal insufficiency

-25% associated with pul hypoplasia

Question 26

what is multicystic dysplastic kidney disease

Answer 26

abdnormal development of renal system

cysts are likely dilations of loop of henle

usually only one kidney is affected

Question 27

what is the urogenital sinus

Answer 27

from ventral cloaca (distal hindgut)

cirtical for bladder & urethral development

Question 28

what are the parts of the urogential sinus

Answer 28

1. vesical part: ​forms most of urinary bladder
2. pelvic part: forms neck of bladder & urethera (female) & prostatic urethera (male)
3. phallic part: forms lining of vaginal vestibule (female) & spongy urethera (male)

Question 29

what is the urorectal septum

Answer 29

seperates the urogenital sinus & anorectal canal

expands & contributes to wall of perinium

seperate the urinary and digestive tracts

Question 30

what are the steps of forming the trigone

Answer 30

week 4-6 mesonephric duct incorporate into post wall of bladder

–> ureteric bud is attached and connects the bud opening into the bladder wall

–> openings of mesonephric duct are carried inferiorly to the pelvic urethra

==> form trigone (region where mesonephric & ureteric ducts blend with post wall of bladder)

Question 31

what are the parts of the bladder and what are they derived from

Answer 31

epithelium - endoderm (urogenital sinus)

submucosa & muscularis = splanchnic mesoderm

trigone = intermediate mesoderm (mesonephric ducts)

Question 32

what is the allantois

Answer 32

continous with bladder - extends from apex of bladder to umbilicus

= fetal mem developed from hind gut –> constricts and forms urachus

will form the median umbilical ligament

Question 33

what is exstrophy of the bladder

Answer 33

arise during body folding in 4th week –> defective closure of the ventral abd wall

expose mucosa of the post wall of bladder

Question 34

what is epispadias

Answer 34

urethral opening is the dorsum of the genital tubercle rather than on ventral side

occurs with extrophy

Question 35

what is the difference btn urachal cysts, sinus & fistulas

Answer 35

urachal cyst: remnant of epithelial lining of urachus bc cord doesnt fill in completely - enlarge & infected

urachal sinus: end of urachus remain open into the inf bladder or umbilius (sup part)

urachal fistula: entire urachus remains patent –> allow urin gto escape from umbilical orifice

Question 36

what are the parts of the suprarenal gland & what do they produce

Answer 36

• Cortex
  
  • zona glomerulosa: mineralocorticoids
  • zona fasciculata: glucocorticoids
  • zona reticularis: sex hormones
• Medulla
  
  • chromaffin cells that secrete NE & Epi

Question 37

what does the medulla of the suprarenal gland develop from

Answer 37

NCCs

they migrate thru intemediate mesoderm to form adrenal medula & differntiate into chromaffin cells

Question 38

how does the cortex of the suprarenal gland form

Answer 38

week 5

coelomic epithelium (somatic mesoderm) delaminate & enter surrouding mesoderm –> then regress in 2nd month PN to make zona glomerulosa, fasciculata & reticularis

fetal cortex will secrete DHEA –> converted to estradiol (*essential for pregnancy*)